Analysis of the Interaction Torque on the Arm Based on Via-Point Movement

To produce a desired movement, the human motor control system must regular the interaction torque generated owing to the multi-joint structure of the body. In this study, the trajectories of human movements were evaluated considering the interaction torque generated through the elbow and shoulder joints. Measurement experiments were conducted, in which the participants performed movements corresponding to a three-point task, and the results indicated that the interaction torque is correlated with certain characteristics of the trajectories of the arm movements. Moreover, the contribution of the interaction torque in realizing the task differs in the cases of dominant and non-dominant hands. In addition, through a simulation, the interaction torque of simulated trajectories was modulated to examine the corresponding effect on the arm movements. For a point-to-point movement, certain characteristics of the actual movements were reproduced in the simulated trajectories. However, for a three-point movement, the characteristics of the simulated trajectories were only partially similar to those of the measured trajectories. The findings indicate that the interaction torque notably influences the motor control, and the tuning of the interaction torque is more complex than the other criteria of motor control

INVESTIGATING KEY FACTORS FOR FEMALE PLAYERS TO GENERATE COMPARABLE INTERACTION TORQUE TO THAT OF MALE PLAYERS

We aimed to clarify the kinetic strategy of female players to achieve comparable motion-dependent interaction torque to that of male players during soccer instep kicking. The kicking leg motion of female and male players was captured at 500 Hz. The interaction torque was decomposed into two components due to the kicking leg and the support leg actions using the procedure of Inoue et al., (2013). Female players exhibited significantly smaller counter-clockwise (positive) interaction torque due to the support leg action while the clockwise (negative) component due to the kicking leg action was significantly suppressed in the latter part of kicking than male players. Our findings suggest coaches and female players should pay more attention to the kicking leg posture during the latter part of the leg swing to maintain their effective action of the interaction torque

PELVIC ROTATION DYNAMICS OF ACCURACY ENHANCED, SUBMAXIMAL EFFORT INSTEP SOCCER KICKING

The purpose of this study was to clarify the kinetic aspects of the pelvic rotation in accuracy enhanced, submaximal effort soccer instep kicking. Fifteen male soccer players conducted instep kicking in a maximal (MAX) effort and a submaximal (SUB) effort with an emphasis on accuracy. Kicking motions were recorded by a motion capture system with a force platform at 500 Hz. The counter-clockwise pelvic rotation decreased significantly in SUB. Also, the interaction torque on the support leg hip joint decreased significantly in SUB. A previous study reported that the interaction torque was the primary factor in producing pelvic rotation. Thus, controlled pelvic rotation seen in SUB is most likely due to a reduced interaction torque acting on the support leg hip joint. It can be considered that to restrain pelvic rotation is a strategy to slow down the foot swing velocity in accuracy enhanced, submaximal effort instep kicking

Inter-Joint Coordination Deficits Revealed in the Decomposition of Endpoint Jerk During Goal-Directed Arm Movement After Stroke

It is well documented that neurological deficits after stroke can disrupt motor control processes that affect the smoothness of reaching movements. The smoothness of hand trajectories during multi-joint reaching depends on shoulder and elbow joint angular velocities and their successive derivatives as well as on the instantaneous arm configuration and its rate of change. Right-handed survivors of unilateral hemiparetic stroke and neurologically-intact control participants held the handle of a two-joint robot and made horizontal planar reaching movements. We decomposed endpoint jerk into components related to shoulder and elbow joint angular velocity, acceleration, and jerk. We observed an abnormal decomposition pattern in the most severely impaired stroke survivors consistent with deficits of inter-joint coordination. We then used numerical simulations of reaching movements to test whether the specific pattern of inter-joint coordination deficits observed experimentally could be explained by either a general increase in motor noise related to weakness or by an impaired ability to compensate for multi-joint interaction torque. Simulation results suggest that observed deficits in movement smoothness after stroke more likely reflect an impaired ability to compensate for multi-joint interaction torques rather than the mere presence of elevated motor noise

Tunable diffusion of magnetic particles in a quasi-one-dimensional channel

The diffusion of a system of ferromagnetic dipoles confined in a quasi-one-dimensional parabolic trap is studied using Brownian dynamics simulations. We show that the dynamics of the system is tunable by an in-plane external homogeneous magnetic field. For a strong applied magnetic field, we find that the mobility of the system, the exponent of diffusion and the crossover time among different diffusion regimes can be tuned by the orientation of the magnetic field. For weak magnetic fields, the exponent of diffusion in the subdiffusive regime is independent of the orientation of the external field.Comment: 9 pages, 13 figures, to appear in Phys. Rev. E (2013